The present invention relates generally to reciprocating compressors. More particularly, the present invention relates to a crankshaft having at least two eccentric members of different diameter and a method of assembling a reciprocating compressor using a crankshaft having at least two eccentric members of different diameter.
Reciprocating compressors are known to have many different configurations. One well known configuration is commonly referred to as an in-line, two-cylinder compressor. In this configuration, the compressor includes a block having a side defining two adjacent cylinders, and a crankshaft having two eccentric members separated by a transfer section. The eccentric members rotatably support respective connecting rod and piston assemblies within respective cylinders of the block.
During operation of an in-line, two-cylinder compressor, a motor rotates the crankshaft resulting in the eccentric motion of each of the eccentric members. As the eccentric members rotate, the respective connecting rod and piston assemblies reciprocate within each of the two cylinders.
One efficient method of assembling an in-line, two-cylinder compressor as described includes assembling the pistons to respective connecting rods. Thereafter, the connecting rod and piston assemblies are inserted into the respective cylinders of the block. After the connecting rod and piston assemblies have been inserted into the block, the crankshaft is inserted into the block such that the eccentric members are inserted through receiving apertures of the connecting rods in ends opposite those to which the pistons are attached.
Another compressor configuration that has been found useful is referred to as the four-cylinder compressor. In one known type of four-cylinder compressor, a block is provided having two opposing sides with each side including two adjacent cylinders. A connecting rod and piston assembly is provided in each cylinder and a crankshaft is provided having two eccentric members each rotatably supporting two connecting rod and piston assemblies located in cylinders on opposite sides of the block. During operation, a motor rotates the crankshaft resulting in an eccentric motion of the eccentric members. As each eccentric member rotates, the two connecting rod and piston assemblies supported on a given eccentric member travel in the same direction in a reciprocating manner.
The crankshaft for a four-cylinder reciprocating compressor must be altered to increase the axial width of the eccentric members so that they each may rotatably support two connecting rod and piston assemblies instead of one. Due to the increased axial width of each eccentric member required for supporting two connecting rod and piston assemblies instead of one, the length of the transfer section between the eccentric members is reduced. When this length is reduced, it becomes more difficult to insert the eccentric members of the crankshaft through the apertures of the connecting rods. This makes it more difficult to assemble the compressor efficiently and economically.
Possible solutions to this problem include reducing the cross-section of the transfer section and/or assembling the connecting rods around the eccentric members after the crankshaft has been inserted into the block. Unfortunately, neither of these solutions is optimum. First, when the cross-section of the transfer section is reduced, the strength and reliability of the crankshaft may also be reduced. Second, assembling the connecting rods around the eccentric members after the crankshaft has been installed in the block requires two-piece connecting rods. The use of two-piece connecting rods increases the number of parts, thereby also increasing the complexity of assembling the compressor. This may result in increased manufacturing costs.
In light of the foregoing, there is a need for a device and method for efficiently and economically assembling a four-cylinder reciprocating compressor.
Accordingly, the present invention is directed to a device and method for efficiently and economically assembling a reciprocating compressor.
According to the present invention, eccentric members on the crankshaft are designed to have different diameters. By providing eccentric members having different diameters, the eccentric member having a smaller diameter is more easily inserted first through the connecting rod and piston assemblies having the larger diameter for accommodating the eccentric member having a larger diameter. The crankshaft is then inserted further, until the smaller diameter eccentric fits within the smaller diameter connecting rod and the larger diameter eccentric fits within the rod to match the larger diameter eccentric. As a result, it is not required that the cross-section of the transfer section be reduced, nor is it required that the connecting rods be of two-piece construction in order for the compressor to be assembled. Consequently, by providing a crankshaft having eccentric members of different diameters, a reciprocating compressor may be more efficiently and economically assembled.
The advantages and purposes of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages and purposes of the invention will be realized and attained by the elements and combinations particularly pointed out in the appended claims.
To attain the advantages and in accordance with the purposes of the invention as embodied and broadly described herein, one aspect of the invention is directed to a crankshaft for a reciprocating compressor. The crankshaft includes an elongated shaft defining a longitudinal axis, a first eccentric member having a first diameter and a first center offset from the longitudinal axis of the elongated shaft. The crankshaft also includes a second eccentric member having a second diameter and a second center offset from the first center and the longitudinal axis of the elongated shaft, with the second diameter being larger than the first diameter. The crankshaft further includes a transfer section connecting the first eccentric member to the second eccentric member, with the transfer section including at least one ramp portion.
In another aspect, the invention provides a compressor including a block defining an internal cavity, at least one aperture in communication with the internal cavity, and at least two cylinders. The compressor further includes a crankshaft received within the internal cavity, with the crankshaft including an elongated shaft defining a longitudinal axis, a first eccentric member defining a first diameter and a first center offset from the longitudinal axis, and a second eccentric member defining a second diameter and a second center offset from the first center and the longitudinal axis. The first diameter is smaller than the second diameter. The compressor further includes a first connecting rod having an aperture defining a diameter substantially equal to the first diameter with the first eccentric member rotatably supporting the first connecting rod. The compressor also includes a second connecting rod having an aperture defining a diameter substantially equal to the second diameter, with the second eccentric member rotatably supporting the second connecting rod.
In yet another aspect, the invention provides a method for assembling a compressor having a block defining an internal cavity, at least one aperture in communication with the internal cavity, and a first cylinder and second cylinder. The method includes inserting first connecting rod into the first cylinder of the block and inserting a second connecting rod into the second cylinder of the block. The method further includes inserting a crankshaft through the aperture in the block, the crankshaft having a first eccentric member having a first diameter and a second eccentric member having a second diameter larger than the first diameter. The method also includes inserting the crankshaft into the block such that the first eccentric member is passed through an aperture of the second connecting rod having a diameter substantially equal to the second diameter of the second eccentric member, and inserting the crankshaft further into the block such that the first eccentric member is received within an aperture in the first connecting rod having a diameter substantially equal to the first diameter of the first eccentric member.
Further, the second eccentric member is received in the aperture in the second connecting rod, whereby the first eccentric member rotatably supports first connecting rod and the second eccentric member rotatably supports the second connecting rod.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.